Door Iris Porthole is the Perfect Fix for Detroit Hackerspace

In order to resolve the problem of congestion at the entrance to their hackerspace, the minds at i3Detroit installed a motion-activated mechanical iris in their door’s porthole.

Grabbing the design online (which they are now hosting on their site here), the parts were laser cut out of wood, gold leaf was added for effect, and it was relatively easy to assemble. PIR sensors detect movement on both sides of the door and an FET resistor connected to an orange LED add some old-school science fiction flair. The iris is actuated by a 12V car window motor — which works just fine on the 5V power that it’s supplied with — and an Arduino filling in as a controller. Start and stop positioning required some limit switches that seem to do the trick.

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Physical Kill Switch For Rogue Applications

Necessity is the mother of invention, but sometimes frustration is as good a motivator. [Maciej] does a bunch of statistics in his day job using SPSS. silaczLike most complicated pieces of software, it can get hung, and the only way to stop it is to manually kill the running processes. Apparently, that happened one time too many for [Maciej].

He took matters into his own hands, repurposing a big red emergency-stop button for the task. It’s mounted on a jar, and the microcontroller inside is configured as a USB keyboard. When he mashes the button, it opens the “Run…” menu and types out taskkill spssengine.exe for him.

We can totally see the therapeutic value of such a device. Plus, in case SPSS is gobbling up his system memory and everything’s approaching standstill, the vital seconds saved by the microcontroller’s quick-typing fingers could be a lifesaver.

Hackaday Prize Entry: Selfie Bot Let’s You Vlog Hands Free

[Sergey Mironov] sent in his SelfieBot project. His company, Endurance Robots, sells a commercial version of the bot, which leads us to believe that in a strange and maybe brilliant move he decided to just sell the prototype stage of the product development as a kit. Since he also gave away the firmware, STLs, BOM, and made a guide so anyone can build it, we’re not complaining.

The bot is simple enough. Nicely housed hobby servos in a 3D printed case take care of the pan and tilt of the camera. The base of the bot encloses the electronics, which are an Arduino nano, a Bluetooth module, and the support electronics for power and motor driving.

To perform the face tracking, the build assumes you have a second phone. This is silly, but isn’t so unreasonable. Most people who’ve had a smart phone for a few years have a spare one living in a drawer as back-up. One phone runs the face tracking software and points the bot, via Bluetooth, towards the user. The other phone records the video.

The bot is pretty jumpy in the example video, but this can be taken care of with better motors. For a proof-of-concept, it works. A video of it in action after the break.

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Digital Opponent In An Analog Package

Unsatisfied with the present options for chess computers and preferring the feel of a real board and pieces, [Max Dobres] decided that his best option would be to build his own.

Light and dark wood veneer on 8mm MDF board created a board that was thin enough for adding LEDs to display moves and for the 10mm x 1mm neodymium magnets in the pieces to trip the reed switches under each space. The LEDs were wired in a matrix and connected to an Arduino Uno by a MAX7219 LED driver, while the reed switches were connected via a Centipede card. [Dobres] notes that you’ll want to test that the reed switches are positioned correctly — otherwise they might not detect the pieces!

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A Pi Robot Without a Hat

Daughter boards for microcontroller systems, whether they are shields, hats, feathers, capes, or whatever, are a convenient way to add sensors and controllers. Well, most of the time they are until challenges arise trying to stack multiple boards. Then you find the board you want to be mid-stack doesn’t have stackable headers, the top LCD board blocks the RF from a lower board, and extra headers are needed to provide clearance for the cabling to the servos, motors, and inputs. Then you find some boards try to use the pins for different purposes. Software gets into the act when support libraries want to use the same timer or other resources for different purposes. It can become a mess.

The alternative is to unstack the stack and use external boards. I took this approach in 2013 for a robotics competition. The computer on the robots was an ITX system which precluded using daughter boards, and USB ports were my interface of choice. I used a servo controller and two motor controllers from Pololu. They are still available and I’m using them on a rebuild, this time using the Raspberry Pi as the brain. USB isn’t the only option, though. A quick search found boards at Adafruit, Robotshop, and Sparkfun that use I2C.

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Venduino Serves Snacks, Shows Vending is Tricky Business

Seems like just about every hackerspace eventually ends up with an old vending machine that gets hacked and modded to serve up parts, tools, and consumables. But why don’t more hackerspaces build their own vending machines from scratch? Because as [Ryan Bates] found out, building a DIY vending machine isn’t as easy as it looks.

[Ryan]’s “Venduino” has a lot of hackerspace standard components – laser-cut birch plywood case, Parallax continuous rotation servos, an LCD screen from an old Nokia phone, and of course an Arduino. The design is simple, but the devil is in the details. The machine makes no attempt to validate the coins going into it, the product augurs are not quite optimized to dispense reliably, and the whole machine can be cleaned out of product with a few quick shakes. Granted, [Ryan] isn’t trying to build a reliable money-making machine, but his travails only underscore the quality engineering behind modern vending machines. It might not seem like it when your Cheetos are dangling from the end of an auger, but think about how many successful transactions the real things process in an environment with a lot of variables.

Of course, every failure mode is just something to improve in the next version, but as it is this is still a neat project with some great ideas. If you’re more interested in the workings of commercial machines, check out our posts on listening in on vending machine comms or a Tweeting vending machine.

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Raspberry Pi Gets Turned On

The Raspberry Pi and other similar Linux-based single board computers simplify many projects. However, one issue with Linux is that it doesn’t like being turned off abruptly. Things have gotten better, and you can certainly configure things to minimize the risk, but–in general–shutting a Linux system down while it is running will eventually lead to file system corruption.

If your project has an interface, you can always provide a shutdown option, but that doesn’t help if your application is headless. You can provide a shutdown button, but that leaves the problem of turning the device back on.

[Ivan] solved this problem with–what else–an Arduino (see the video below). Simplistically, the Arduino reads a button and uses a FET to turn off the power to the Pi. The reason for the Arduino, is that the tiny processor (which draws less than a Pi and doesn’t mind being shut down abruptly) can log into the Pi and properly shut it down. The real advantage, though, is that you could use other Arduino inputs to determine when to turn the Pi on and off.

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